Surge protective devices can be used to assist in protecting loads from electrically induced damage. Surge protective devices are typically designed to deal with short duration, high magnitude voltage and/or current events on the electrical wiring system. These events can last from several microseconds to several milliseconds and can be attributable to, for instance, switching loads on and off, lightning strikes, equipment failures, faults, etc. A surge protective device can absorb these events by clamping them to more manageable magnitudes. In this process, a surge protective device can heat up and eventually wear out.
There can be other events that can occur in an electrical system that can negatively affect load life and that may not be mitigated by a surge protective device. For example, an electrical system can exhibit voltage sags or swells. Electrical systems typically exhibit non-linear, reactive characteristics that can cause various undervoltage events, overvoltage events, oscillations, and/or some combination thereof which can be transient or even of longer term duration. One detrimental event can be a long duration, abnormal overvoltage condition, (e.g., swell). Loads are rated for operation on an electrical wiring supply and system at a particular nominal voltage, but usually are specified to work in a tolerance range around the nominal voltage. Experiencing an overvoltage condition for an extended period of time above the high side tolerance can cause some loads to be damaged.